1. Field of the Invention
The present invention relates to a method of and an apparatus for manufacturing a self-developing instant photography film unit.
2. Description of the Related Art
With the recent popularity of instant cameras, self-developing instant photography film units are being mass-produced. An instant photography film unit comprises a mask sheet having an image frame which defines a picture size in its center, a photosensitive sheet having a photosensitive layer coated on a transparent or opaque support layer, a transparent sheet for extending a developing solution between itself and the photosensitive sheet, and a pair of rails or spacers disposed between the photosensitive sheet and the transparent sheet for defining a gap therebetween for the passage of the developing solution therein. A pod or container which stores the developing solution and a trap for trapping an excessive developing solution are attached to the mask sheet at respective opposite side edges of the image frame of the mask sheet.
Various types of instant photography film units have been known in the art. For example, according to one type of instant photography film unit, the photosensitive sheet is joined to the upper surface of the mask sheet, and the transparent sheet is joined to the upper surface of the photosensitive sheet by the rails interposed therebetween, and the pod and the trap are wrapped in the side edges of the mask sheet that are folded onto the transparent sheet perpendicularly to the rails. According to another type of instant photography film unit, the photosensitive sheet and the transparent sheet are stacked in a given order on the mask sheet, and the rails are attached so as to extend from the photosensitive sheet to the transparent sheet, and the pod and the trap are attached to the mask sheet perpendicularly to the rails.
There have been proposed various processes for manufacturing an instant photography film unit. For example, Japanese patent publication No. 62-55772 discloses one such proposed process for manufacturing an instant photography film unit. According to the disclosed process, as shown in FIG. 11 of the accompanying drawings, sheets 1, 2, one of which is a photosensitive sheet whereas the other is a transparent sheet, are joined to each other by a joining unit 3, and a rail web 4 is cut into a rail 5 that is heat-sealed over the sheet 2, which is wider than the sheet 1, transversely across the sheet 1.
The joined sheets 1, 2 are then cut along the central line of the rail 5 by a cutter 6, and then bonded to a mask sheet 8 by a heat sealer 7. In a peripheral edge joining station 9, the entire edge of the sheet 2 is bonded to the mask sheet 8 in surrounding relationship to an image zone opening defined in the mask sheet 8. In an attaching station 10, a solution pod 11 and a trap 12 are bonded to respective opposite sides of the mask sheet 8, and thereafter folded onto the opposite sides of the mask sheet 8 in a folding station 13. Then, the assembly is sealed in a sealing station 14, and the mask sheet 8 is cut off in a cutting station 15, thus producing an instant photography film unit.
The conventional arrangement requires that the worker store a certain number of manufactured instant photography film units into a case. In order to prevent the instant photography film units from being irradiated with extraneous light, the worker needs to package the instant photography film units in a dark chamber. Therefore, the packaging process has been considerably tedious and time-consuming. Accordingly, the process of packaging the manufactured instant photography film units to produce film unit packages has been considerably cumbersome and makes it impossible to perform the entire manufacturing process efficiently.
The sheets 1, 2 and the mask sheet 8 are exposed to temperature changes and humidity changes in the heat sealing process. Particularly, the photosensitive sheet is susceptible to humidity, and tends to shrink in the manufacturing process. When the sheets 1, 2 shrink, the mask sheet 8 to which these sheets 1, 2 are attached is displaced in the direction in which it is fed, making it difficult to attach the pod 11 and the trap 12 in accurate positions with respect to the opening in the mask sheet 8, and the instant photography film units tend to be severed at different positions. As a consequence, it is impossible to manufacture high-quality instant photography film units.
According to the above conventional method, the pod 11 and the trap 12 are bonded by heat sealing after they have been supplied one to each side of the mask sheet 8. Therefore, it is time-consuming to join the pod 11 and the trap 12, and hence the entire process for manufacturing instant photography film units cannot be made more efficient.
In the above manufacturing method, the pitch time of each of the steps, particularly those steps requiring heat bonding, ranging from the supply of the sheets 1, 2 to the completion of instant photography film units, is relatively long. Since the pitch times of the steps are determined on the basis of the pitch times of the heating bonding steps, undesirable idle times are present in the entire process, making it impossible to carry out the entire process for manufacturing instant photography film units efficiently.
After the joined sheets 1, 2 have been cut along the central line of the rail 5, the sheets 1, 2 are bonded to the mask sheet 8. Therefore, a structure is required for accurately positioning the severed sheets 1, 2 on the mask sheet 8. The positioning structure makes the entire system and process complex, and also makes the cost of manufactured instant photography film units high.